1. Field of the Invention
This invention relates to a substrate processing method and a substrate processing apparatus for performing a cleaning process on various substrates such as semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical discs, substrates for magnetic discs and substrates for magneto-optical discs (hereinafter, merely referred to as “substrates”).
2. Description of the Related Art
A production process of electronic components such as semiconductor devices and liquid crystal displays includes a process of forming a fine pattern by repeatedly performing processes such as film formation on a top surface of a substrate and etching. Here, the top surface of the substrate needs to be kept clean to satisfactorily perform microfabrication, and a cleaning process is performed on the substrate top surface if necessary. For example, in an apparatus disclosed in JP-A-2008-71875, after a liquid such as deionized water (hereinafter referred to as “DIW”) is supplied to a substrate top surface and frozen, the frozen liquid is melted and removed by a rinsing liquid to clean the substrate top surface.
That is, the following process is performed in the apparatus disclosed in JP-A-2008-71875. First, a liquid film of DIW is formed on the entire substrate top, surface by supplying the DIW to the top surface of the substrate. Subsequently, the supply of the DIW is stopped and a low-temperature nitrogen gas is supplied to the substrate top surface to freeze the DIW. This causes the DIW having penetrated between contaminants such as particles and the substrate top surface to become ice and expand, whereby the contaminants such as particles are separated from the substrate by an infinitesimal distance. Further, by expanding in a direction parallel to the top surface of the substrate, particles and the like adhering to the substrate are peeled off. As a result, adhesion between the substrate top surface and the contaminants such as particles is reduced and, further, the contaminants such as particles are detached from the substrate top surface. Thereafter, by melting and removing the ice on the substrate top surface by DIW as a rinsing liquid, the contaminants such as particles can be efficiently removed from the substrate top surface.
To produce a low-temperature nitrogen gas, a method for causing a nitrogen gas to flow in a pipe immersed in liquid nitrogen stored in a container and cooling the nitrogen gas by heat exchange is performed as in an apparatus disclosed, for example, in JP-A-2010-123835.